There are cases in which, for example, conventional engine systems are provided with a power supply line (for example, an AC 200 V line for those customized for Japan, and an AC 230 V line or AC 240 V line for those customized for Europe) with which a power supply voltage from an alternating-current power supply is supplied and a system line (for example, a DC 24 V line) with which a voltage obtained as a result of reduction of the power supply voltage from the alternating-current power supply is supplied.
Generally, with the system line, the power supply voltage (for example, AC 200 V for those customized for Japan) from the alternating-current power supply is reduced by a transformer, and an alternating voltage obtained as a result of the voltage reduction by the transformer is rectified to give a direct current voltage (for example, DC 24 V). The system line is usually connected to a starter motor for starting an engine. Other examples that can be connected to the system line include a control apparatus and an electrical device such as a relay or a solenoid valve.
Examples that can be connected to the power supply line include a power receiving device such as a motor of a cooling water pump or a cooling fan, that receives the voltage supplied from the alternating-current power supply.
When producing engine systems intended for different destinations, from the viewpoint of reducing the production cost, attempts have been made to use as many common constituent elements as possible in the systems regardless of the destination. In other words, in order to change the specification (for example, AC 200 V for those customized for Japan, or AC 230 V or AC 240 V for those customized for Europe) of the power supply voltage from the alternating-current power supply depending on the destination (for example, Japan or Europe), efforts have been made to minimize changes of the constituent elements in the engine systems.
With respect to the system line, for example, an autotransformer that shares a part of winding between the primary and the secondary is used as a transformer to which the power supply voltage from the alternating-current power supply is supplied, the power supply voltage whose specification is to be changed is input across two terminals in a shunt winding path and across two terminals in a path of the primary (for example, AC 200 V across the terminals in the shunt winding path for those customized for Japan, and AC 230 V or AC 240 V across the terminals in the path of the primary for those customized for Europe), and a constant voltage (for example, DC 24 V) is output by the secondary, whereby the specification of the power supply voltage from the alternating-current power supply can be changed depending on the destination.
Patent Document 1 is an example of the reference documents in the relevant technical field. Specifically, Patent Document 1 discloses a secondary voltage regulation circuit that is made up of a combination of an autotransformer, which shares a part of winding between the primary and the secondary, and a variable alternating-current power supply, and that is configured such that the voltage on the load side, specifically, the voltage of the secondary remains constant even when there is a change in the voltage on the alternating-current power supply side, specifically, the voltage of the primary.
With respect to the power supply line, on the other hand, basically, the voltage supplied from the alternating-current power supply is directly supplied to the power receiving device. Accordingly, in order to change the specification of the power supply voltage from the alternating-current power supply depending on the destination, it is necessary to provide an additional transformer between the transformer used by the system line and the alternating-current power supply. This configuration enables the specification of the power supply voltage from the alternating-current power supply to be changed depending on the destination, but it would increase the production cost accordingly. Nonetheless, if the specification of the power supply voltage from the alternating-current power supply is not changed for the power supply line, it would cause harmful effects on the performance of the power receiving device or the operation of the power receiving device.
In particular, in the case where the power supply voltage whose specification is to be changed is higher (for example, AC 230 V or AC 240 V for Europe) than the expected voltage (for example, AC 200 V, which is a voltage allowed by the power receiving device customized for Japan), a voltage exceeding the allowable voltage is supplied to the power receiving device, and therefore it is not desirable.
Under such circumstances, there is demand to change the specification of the power supply voltage from the alternating-current power supply depending on the destination by using the transformer used by the system line without providing an additional transformer to the power supply line.
Prior Art Document
Patent Document
[Patent Document 1] JP 11-164559A